This invention relates to sheet handling and processing mechanisms.
Sheet handling and processing mechanisms are employed in conventional automatic electrostatographic imaging systems. For instance, a single sheet is fed onto an electrophotographic drum where the developed image is transferred from the drum to the sheet. After the transfer step is completed, the sheet is stripped from the drum.
There are several known methods by which a sheet is separated from a drum; for example, that shown in U.S. Pat. No. 3,062,536 to Rutkus. This mechanism employs a manifold having a multiple outlet conduits or nozzles directed against the surface of the electrostatographic drum so that jets of compressed aeriform fluid from the nozzles are directed against the leading edge of the sheet being transferred to blow the edge of the sheet off the drum. In this system the remainder of the sheet being transferred is then peeled from the drum due to its own weight. The manifold is supplied with compressed aeriform by means of a pulsator or similar source of compressed aeriform fluid.
Another method utilizes mechanical arms which are physically inserted between the sheet and the conveyor surface. This type of apparatus is normally programmed so that the arm is placed against the drum surface as the sheet approaches the vicinity of the stripping area. When the sheet meets the arm, it is physically separated from the conveyor surface by the arm being inserted between the two. To assure that the sheet is always separated and diverted from the drum, the tip of the arm usually travels in recesses on the drum surface so that there is no possible way the sheet can move past the arm. An improvement in this type of system is described in U.S. Pat. No. 3,450,402 to Weiler. This apparatus consists of an arm carrying a multitude of wedge shaped fingers located adjacent to and spaced across the path of travel of the sheet being carried by the conveyor surface. The fingers are biased against the conveyor surface when the leading edge of the sheet reaches the vicinity of the fingers to cause separation of the sheet from the drum. After the leading edge of the sheet is separated, the arm rotates moving the fingers and the edge of the sheet away from the conveyor surface.
Whatever form of sheet stripping mechanism is provided, it is desired that the sheet or copy carrying medium which could be of continuous web form, continues to strip from the conveyor or drum surface. In many instances the copy carrying medium will continue to strip under the action of its own weight after its leading edge has been separated by one form of stripping device or another. However, in some instances we have found that the copy carrying medium does not continue to strip satisfactorily along its length under the action of gravity alone. In other instances, the copying apparatus is so positioned that the action of gravity is not in a direction that assists the stripping action and may even be acting counter to the desired direction for such stripping action.